Ultrasensitive Mechanoluminescence Materials by Controlling Molecular Aggregation State via Different Alkyl Groups

Organic mechanoluminescence (ML) materials have drawn considerable research attention in the past few years due to their diverse applications in many fields. However, owing to the absence of a rationally designing concept at molecular level, the ML-active organomaterials with ultrasensitivity have been scarcely reported. In this contribution, alkyl groups with different steric hindrances were introduced into triphenylamine (TPA) derivatives' skeleton, resulting in six compounds as TPA-CHO, MTPA-CHO, ITPA-CHO, sTTPA-CHO, TTPA-CHO, and dTTPA-CHO. Through detailed analysis of their crystal structure and theoretical calculations, it was affirmed that the presence of alkyl groups in TPA derivatives leads to a range of aggregation states, which manage the TPA derivatives with or without ML performance. Contrast to various analogues, TTPA-CHO exhibited bright and the most sensitive ML performance under a mechanical force stimulation of 0.1 N. Based on the ultrasensitive ML characteristic, the applications of information storage and encryption were successfully demonstrated.